When building a formula of a big table with lots of columns there is no easy way to see all the columns, many times the formula editor itself is obstructing view of columns or other relevant content that would be essential to see to complete the formula.
The list of suggested columns is not enough, sometimes you have to do a little bit of tricks to try to trigger the suggestions to appear (if the formula has errors as it is incomplete etc) and sometimes you need to see the actual column values to remember the correct column.
This would be similar how Excel works. When you are editing a cell, Excel allows scrolling the content behind.